1. Field of the Invention
This invention relates to the field of separation of gas mixtures and particularly to the separation of a single component from a mixture of gases. A semipermeable membrane and a purge gas are used. The purge gas contains at least one of the gases desired to be retained on the feed side of the membrane. The purpose of this is to minimize the passage across the membrane of the gases to be retained and encourage the passage across the membrane from the feed side to the purge side of the gas component to be separated.
2. Description of the Prior Art
The prior art has separated gases from mixtures using semipermeable membranes from a feed side to a diffusion side by drawing a vacuum on the diffusion side.
Another method commonly used is to pass a feed gas on one side of a semipermeable membrane and to pass a purge gas on the opposite side. A higher pressure is used for the feed gas than for the purge gas to encourage the diffusion of molecules from the feed side to the purge side. If the concentration of the desired gases to be diffused is less on the sweep side, then the differential in pressure will cause diffusion of such gases from the feed side to the purge side. Unfortunately the method does not permit the passage of a single element from a mixture of gases since generally the partial pressure of all the components on one side of the membrane are less on the sweep side as well as the concentration thereof.
Another method includes using a very thin semipermeable membrane which is selectably permeable for a specific gas such as hydrogen. In this instance, the feed gas is passed in contact with the semipermeable membrane and only the molecule which is selectively permitted to pass will go through the membrane. This method has limited application since such highly selective membranes are limited to very few gas elements at the present time.